A typical gas fired appliance, such as a. boiler, includes a gas burner for generating heat. For example, with a boiler the burner is used for heating water. The appliance typically includes a draft hood or diverter. A vent from the draft hood exhausts products of combustion from the appliance. The vent may include a flue damper.
The typical known analog damper control system has proven to be a safe and reliable accessory for fuel fired appliances such as water heaters, furnaces, and boilers. For simplicity, the terms “heat system” and “appliance” are a reference to “fuel fired appliance”. A simple heat system is defined as a fuel fired appliance that has analog inputs and outputs for use with a damper system to control the fuel delivery solenoid valve. A smart heat system is defined as a fuel fired appliance that does not have analog inputs and outputs for use with a damper control system.
The analog damper control improves the overall efficiency of a simple heating system by closing the flue when the heat system is idle. The analog damper control incorporates a proving circuit that prevents heat activity of the appliance when the damper gate is not in the open position. The proving circuit in simplistic terms may include a positioning cam or lever attached to a mechanical switch that would electrically connect or disconnect the heat control signal to the “fuel delivery” solenoid valve in relationship to the damper gate position. A heat call by the appliance would initiate the damper control to open the damper gate. When the damper gate is in the open position, the proving switch will be in the closed position to allow current flow from the appliance to the “fuel delivery” solenoid valve. The proving circuit is a safety switch that would prevent release and firing of fossil fuel when the damper is not fully open. A typical damper control system is shown in the diagram of FIG. 1.
More recently, fuel fired appliances have become more complex in design. Introduction of new technology has evolved the simple heat system to a modern smart heat system. Many of the smart heat systems do not have provisions for the simple analog damper control. Analog control signals have been replaced by a serial network interface to transfer data from the smart heat system to accessory components such as a damper control system.
One known method that can be used to implement an integrated damper control with a smart heat system is to operate the damper as a heat anticipator. Data that is transferred between the smart heat system and accessory component could include; set point, temperature, heat activity data, remote set point, and operating differential. The integrated damper control reads data from the smart heat system through the serial interface to determine when to open or close the damper gate. The operating temperature, set point and differential will be used to calculate the operating point or anticipated heat turn on temperature. The anticipated value will predict when heating will occur. The heat activity or “heating status” of the smart heat system will also be monitored. When the temperature is close to the anticipated value, the integrated damper control will send a. low set point data instruction to the smart heat system to suspend any heat call activity while the damper is transitioning to the open. position. Once the damper has verified the damper gate is open, the original set point will be transmitted to the smart heat system to allow for heating to occur. In the event the smart heat system activates the fuel solenoid valve while the damper is closed, the integrated damper control will momentarily suppress the operating set point of the smart heat system through the serial interface to deactivate the heat call. The integrated damper will open the damper gate and then restore the smart heat system's set point to allow the heat call to commence. The “heating status” register will be monitored during the heat call to determine when the heat call has been satisfied. Once the heat call terminates, the damper will be closed.
There are issues with the heat anticipation method such that it is possible for the smart heat system to activate the fuel delivery solenoid while the damper gate is in the closed position, which is not permitted by the safety standards covering fuel fired appliances.
This application is directed to improvements in damper control systems.